In typical venetian blinds having a number of slats held in an aligned state, lifting/lowering cords for lifting and lowering the slats extend penetrating a lifting/lowering cord insertion hole formed in a central portion in a back and forth (transverse) direction of each slat, and an end of the lifting/lowering cord passing through each slat is connected to a bottom rail provided below the slats. The bottom rail is lifted and lowered by the lifting/lowering cords to lift and lower the slats.
Meanwhile, as a venetian blind in which the lifting/lowering cords are disposed at a position offset from the central portion in the back and forth direction of each slat, there have been known the venetian blinds disclosed in Patent Literatures 1 and 2.
In the venetian blind disclosed in the Patent Literature 1, each slat has side edge cut-out portions on both side, with which vertical cords on both side of a ladder cord are adapted to be engaged. By virtue of the engagement between the vertical cords on both-side and the cut-out portions, the slats are positioned in a back and forth direction, and lateral deviation of the slats in the slat longitudinal direction is prevented. At least one lifting/lowering cord is located on one side of the venetian blind in the back and forth direction thereof, and the other lifting/lowering cord is located on the other side of the venetian blind in the back and forth direction thereof. Those lifting/lowering cords are disposed along the vertical cords of the ladder cord to be inserted through loops extended from the vertical cords, and, thus, to connect their one ends to the bottom rail. The other end of the lifting/lowering cords are led in a head box to an end portion of the head box in the longitudinal direction by a guide roller or the like and led out of the head box through a stopper device. When the lifting/lowering cords led out of the head box are lowered, the bottom rail is lifted, and the slats are piled up in sequence from the bottom by the bottom rail. Meanwhile, when the stopper device is released by operating the lifting/lowering cords, the bottom rail and the slats are lowered by their own weights.
As described above, in the venetian blind disclosed in the Patent Literature 1, the lifting/lowering cords are located at the side edge portions of the slats, and the slats do not have any hole through which the lifting/lowering cords are inserted, it is therefore possible to prevent light leakage when the blind is in light shielding state, and, at the same time, because the lifting/lowering cords are disposed in a distributed manner in terms of the back and forth direction, it is possible to prevent the bottom rail from tilting.
In the venetian blind disclosed in the Patent Literature 2, a transverse cord portion of a ladder-shaped supporting cord is constituted of two cords which are arranged in parallel with vertically slightly spaced apart, and a substantially U-shaped cut-out portions are provided at both side edges of a slat at a position supported by the ladder-shaped supporting cord. In order to support the slat by the transverse cord portion of the ladder-shaped supporting cord, the vertical relationship between the two cords of the transverse cord portion is reversed upside down so that cord crossing portions at which the two cords vertically crosses are formed at the both ends of the transverse cord portion. The crossing portions are engaged with the U-shaped cut-out portions of the slat, and the lifting/lowering cord for lifting and lowering the slats is provided along a vertical cord portion of the ladder-shaped support cord on one of outer sides of the slat.
According to the above constitution, in the slats having no hole through which the lifting/lowering cord is inserted, the slats are held between the vertically crossing cords of the transverse cords, and the crossing portions of the transverse cords are engaged with the U-shaped cut-out portions formed at the both side edges of the slat; therefore, the movement of the slats in the horizontal direction can be restricted.